1. Field of the Invention
The present invention relates to a liquid crystal display and driving method thereof, and more particularly, to a liquid crystal display that is capable of reducing power consumption and improving its picture quality in addition.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls light transmittance of a liquid crystal with dielectric anisotropy using an electric field to display a picture. To this end, the LCD includes a liquid crystal display panel having liquid crystal cells arranged in a matrix type and a driving circuit for driving the liquid crystal display panel.
Liquid crystal cells within the LCD panel control light transmittance in accordance with the pixel signal to display a picture. The driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, a timing controller supplying a timing control signal and pixel data to the gate driver and the data driver, and a power source supplying power.
For instance, as shown in FIG. 1, a liquid crystal display includes a liquid crystal display panel 2 having liquid crystal cells Clc arranged in a matrix type, a gate driver 4 for driving gate lines GL1 to GLn of the liquid crystal display panel 2, and a data driver 6 for driving data lines DL1 to DLm of the liquid crystal display panel 2.
In FIG. 1, the LCD panel 2 includes liquid crystal cells Clc and thin film transistors (TFTs), each of which are provided at a crossing between the n gate lines GL1 to GLn and the m data lines DL1 to DLm. The TFT applies a video signal from the data line DL1 to DLm to the liquid crystal cell Clc in response to a scanning signal from the gate lines GL1 to GLn. The liquid crystal cell Clc can be expressed equivalently as liquid crystal capacitors Clc including a pixel electrode connected to the TFT, a common electrode opposed to the pixel electrode, and liquid crystal between the pixel electrode and the common electrode.
The gate driver 4 sequentially applies a scanning signal to the gate lines GL1 to GLn to drive the TFT connected to a corresponding gate line.
The data driver 6 converts pixel data into analog pixel signals to apply video signals for one horizontal line to the data lines DL1 to DLm during one horizontal period when a gate signal is applied to the gate line GL. In this case, the data driver converts the pixel data into pixel signals with the aid of gamma voltages from a gamma voltage generator (not shown) to supply them.
In order to prevent the deterioration of the liquid crystal and to improve the display quality of the picture, such a liquid crystal display is driven in an inversion driving method such as frame inversion system, line (or column) inversion system or dot inversion system.
In the frame inversion system, polarities of the liquid crystal cells are same within one frame and inverted whenever a frame is changed. Such frame inversion system has a problem that flickers occur by frames.
In the line inversion system, polarities of the liquid crystal cells are inverted by horizontal lines and frames as shown in FIG. 2A and FIG. 2B, respectively. Such a line inversion system has the problem that there may be crosstalk between the liquid crystal cells in a horizontal direction, causing flicker in a horizontal stripe pattern.
In the column inversion system, polarities of the liquid crystal cells are inverted by vertical lines and by frames as shown in FIG. 3A and FIG. 3B, respectively. Such a column inversion driving system has the problem that there may be crosstalk between the liquid crystal cells in a vertical direction, causing flicker in a vertical stripe pattern.
In the dot inversion system, as shown in FIG. 4A and FIG. 4B, the polarities of liquid crystal cells are oppposite to those of the horizontally or vertically adjacent liquid crystal cells and are inverted in each subsequent frame.
In other words, in the dot inversion system, pixel signals are supplied to each liquid crystal cell for their positive(+) polarity and negative(−) polarity to appear alternately as it goes from the left upper liquid crystal cells into the right liquid crystal cells and into the lower liquid crystal cells, as shown in FIG. 4A, at the odd-numbered frames; and pixel signals are supplied to each liquid crystal cell for their negative(−) polarity and positive(+) polarity to appear alternately as it goes from the left upper liquid crystal cells into the right liquid crystal cells and into the lower liquid crystal cells, as shown in FIG. 4B, at the even-numbered frames
Such a dot inversion driving system offsets flicker occurring between the adjacent liquid crystal cells in vertical and horizontal directions, thereby providing improved picture quality in comparison to other inversion systems.
However, the dot inversion driving system has a disadvantage in that, because the polarities of the pixel signals applied from the data driver to the data lines should be inverted in the horizontal and vertical directions, a variation in the amount of the pixel signal, that is, the frequency of the pixel signals is larger than in other inversion systems, which causes an increase in power consumption.